Defense Department

Alexander could be called one of the most powerful men in cyberspace. As the director of the National Security Agency, he presides over a massive surveillance apparatus now under scrutiny thanks to revelations of widespread eavesdropping by leaker Edward Snowden. And as head of the Pentagon's Cyber Command, he oversees thousands of U.S. hackers charged with protecting American networks and seeking out vulnerabilities in the online defenses of other states. Alexander, 61, attended West Point and began his career as an Army intelligence officer stationed in Germany. Although he expected to serve for only five years, he wound up spending most of his career in the military. He was the First Armored Division's chief intelligence officer during the Persian Gulf War, and he found a key role in the 2000s handling intelligence for the wars in Afghanistan and Iraq. Along the way, the Syracuse, N.Y., native collected academic degrees like battlefield honors. He holds an M.B.A. from Boston University and advanced degrees in electronic warfare and physics from the Naval Postgraduate School. From the National Defense University, Alexander earned a master's in national security strategy.